Arc chute



June 15, 1948. w. M. SCOTT, JR

ARC CHUTE 2 Sheets-Sheet 1 Filed Jan. 12, 1945 VINVENTOR.

M [0077 JR.

June 15, 1948' w. M. SCOTT, JR 2,443,521

ARC CHUTE Filed Jan. 12, 1945 2 Sheets-Sheet 2 2/ (own I] I; 25 y 2 2627 INVEN TOR.

WVMJUTZ JR.

ATYWRNE).

Patented June 15, B48

ARC CHUTE William M. Scott, Jr., Bryn Mawr, Pa., aasignor to I-T-ECircuit Breaker Company, Philadelphia, Pa., a corporation ofPennsylvania Application January 12, 1945, Serial No. 572,555 6 Claims.(Cl. 200-147) My present invention relates to circuit interrupters andmore particularly to a novel are quencher therefor comprising aplurality of spaced plates of insulating material arranged above andparallel to the arc, the said plates being intersected by a number oftransverse staggered metallic strips or bars.

In my application Serial No. 550,179, filed August 19, 1944, I show asubstantially similar arc chute having a plurality of insulating arcextinguishing plates arranged substantially parallel to the path ofmovement of the arc with a numbe;- of transverse metallic pins or rodsintersecting and being supported by the insulating plates.

My present invention covers a construction in which the metallic memberswhich intersect and are supported by the spaced insulated platescomprise a plurality of narrow copper strips or bars arranged with theirnarrow edges directed substantially toward the arc.

In the construction and operation of circuit interrupters, it isfrequently necessary to provide means for extinguishing quickly the arewhich is drawn between the contacts as they separate. Such circuitinterrupters, which may be tripped open on the incidence of highcurrents, comprise a pair of main contacts (to carry the full currentduring normal operation), which are arranged to make after and breakbefore a. pair of parallel arcing contacts so that any arcing which mayoccur will not pit or otherwise destroy the contact surfaces of the maincontacts.

The are which is drawn between the arcing contacts when they separateunder overcurrent conditions is blown upwardly by blow-out means,

such as a magnetic blow-out or air blast (both well known in the art)into an arc chute which is arranged to quench the are by lengthening thesame or cooling it, by a combination of these methods or in many otherways.

Arc chutes having spaced insulating plates to lengthen the arc orsqueeze the are into narrow slots are well known. Arc chutes whichconsist of spaced metallic plates or their equivalent which break thearc up into a number of small arcs in series and move the are rapidlyacross cooling surfaces, are also well known.

My invention contemplates as its essential function the provision of anarc chute which utilizes both the principle of an arc chute whichutilizes both the principle of spaced insulating plates to lengthen andsqueeze the arc, together with a series of metallic surfaces with whichthe arc is brought into contact and broken up into a series of smallarcs and cooled.

More specifically, my invention contemplates a plurality of spacedinsulating plates extending in a direction parallel to the path of theare into which the arc is forced by blow-out means, the said spacedinsulating plates being used in combination with a series of transversemetallic members which will break the are into a plurality of arcs inseries and will also further cool the same.

Still more specifically, my invention contemplates that these metallicsurfaces be formed by a series of transverse copper strips or bars, eachof which extends through all of the insulating plates and each of whichfurnishes a conductive path between the various slots defined by thespaced insulating plates. These strips or bars are arranged so thattheir edges are substantially directed toward the are as it moves in itspath through the chute.

Accordingly, the primary object of my invention is the formation of anovel are chute comprising spaced insulating plates together with spacedmetallic members, the said plates and members extending in planessubstantially normal to each other.

Another object of my invention is the provision of an arc chute havingspaced insulating plates and extending in planes substantially parallelto that in which the arc is drawn, said plates being intersected by aplurality of transverse strips or bars of highly conductive material,the said strips or bars being so arranged that their edges are directedtoward the arc as the arc moves along its path within the arc chute.

Another object of my invention is the mounting of the transverse stripsor bars by means of insulating plates, where said strips or bars neednot be supported by the side walls oi-the arc chute and may even bespaced therefrom and the mounting of the strips or bars so that they areclosely adjacent to the arc.

Another object of my invention is the provision of novel blow-out meanswhich includes the formation of certain of said strips or bars offerrous material and arranging them so that they will co-act withferrous plates on the sides of the arc chute to form a U-shaped magneticpath.

These and many other objects of my invention will become apparent in thefollowing description and drawings in which:

Figure 1 is a View in perspective partially broken away of my novel arechute.

Figure 2 is a. side view in perspective partially broken away showingthe outside of my are ya chute.

Figure 3 is a front view of my novel are chute taken along line 3-3 ofFigure 1.

Figure 4 is a longitudinal section through one of the special ferrousstrips or bars of my novel are chute taken along line fl-l of Figure 3.

Figure 5 is a cross-sectional view taken on line 5-5 of Figure 4.

Figure 6 is a diagrammatic view of a slightly modified form of arcchute.

Referring now to Figures 1, 2 and 3, there is here shown an arc quencherit having generally the construction and operation of the arc quenchershown in my Patent No. 2,348,228, dated May 9, 1944, assigned to theassignee of the present invention. The are chute 26 comprises a pair ofside supporting plates 2 I, 2! of insulating material, between which aremounted a number of spaced arc extinguishing plates 23, 2 3, 25, 26, 21,also of insulating material. The plates are integrated as a single unitby the transverse bolts 30, 31, 32, 33, which are provided withinsulated bushings 35, 35.

Rivets 30 and Bi are also provided with individual insulating washers orspacers 3'1, 81 to maintain the spacing between the insulating plates atthe front of the arc quencher. Bolts 32 and 33 carry a set of insulatingspacers 38 between each pair of plates which serve to space the backends of the plates from each other; the said spacers 38 also each havinga hook-shaped extension 39 to engage a hook dd on the upper end of thearcing horn M, which is secured to the back panel 32 on which thecircuit breaker is mounted. The plates 23-22 are accordingly insulatedfrom each other and from the side plates 2!.

The side plates 2 i, 2i also carry between them on the transverse boltstit and 65 the opposite arcing horn 36. The said arcing hornll has anextension il carrying a bolt 58 which may be secured to the stationaryflange member all carried by the transverse insulating bridging support50* in order to secure the arc chute in position. A conductiveconnection is made to the arcing horn at through the flange member 59and the pigtail 52.

The are quencher 2b is particularly characterized by a large number oftransverse copper strips or bars 60 which pass through slots in plates23 through 27, as shown in Figures 1 and 8, and which are supportedthereby.

The strips or bars 56 preferably do not contact the upper supportinginsulating members or walls 2!, 2!. This will facilitate assembly andadjustment of the units, permits the strips or bars to be brought downto the contact which form the arcs, and removes the possibility ofbreakdown orcreepage along the supporting plates 2|, 2|. The remainderof the structure corresponds to the circuit breaker shown in my PatentNo. 2,348,228 and in my application Serial No. 550,179.

Essentially the circuit breaker here shown comprises a lower backconnection stud (not shown) to which the main movable contact 12 (on thecontact arm 65) the arcing horn 46-61, and the arcing contact 18 areconnected respectively by a pigtail (not shown), pigtail 52 and pigtail6B. The circuit breaker also comprises an upper back connection stud 10to which is secured the main stationary contact H, which engages themain movable contact 12 mounted on the contact arm 65 to complete acircuit from the upper to the lower connection studs.

When the main contacts H and 12 have separated, while the arcingcontacts hereinafter described are engaged, current flows from the backconnection stud Ill through the conductive bracket 13, to the lower endof the arcing horn M and to the stationary arcing contact 11, then tothe movable arcing contact 78 mounted on the contact arm 55, and thenthrough the pigtail 66 to the lower back connection stud.

As arcing contacts W and 18 separate, an arc is drawn therebetween. Asthe opening movement is completed, the root of the are at contact 11 isblown upwardly along the arcing horn fill while the root of the are atmovable arcing contact 18 is transferred to arcing horn 38 and blownupwardly thereon. The blow-out means, hereinafter more specificallydescribed, blows the center of the arc upwardly into the center of theplates 23 to 21. The plates 23 to 21 are longest in a vertical directionat plates 23 and 27; that is, the downwardly extending cusps 86 thereofextend further downwardly in the case of these plates. The center plate25 has the shortest cusp 82. The intermediate plates 26 and 26 havecusps ti of intermediate length, as shown more particularly in Figure 2and in dotted lines in Figure 1.

Thus in a transverse direction the plates of the arc chute present aV=shape which tends to guide the arc toward the center of the chute. Thedownwardlyextending cusps 8B, and 82 intercept the center of the arc andtend to guide the arc in its upward movement to squeeze into theconfined space between the plates.

The arc in being driven upwardly tends to be squeezed into but one ofthe spaces; for instance, in. the space 85 between plates 26 and 25 orin the space 86 between plates 25 and 26. It is not necessarily confinedto either or both Of these spaces but may be broken up into a pluralityof parallel arcs in separate spaces.

While this type of are chute having only the spaced insulating plates 23to 27 has been effective in use, it has been found that perhaps only oneor two of the spaces, and usually only one, are actually eifective inextinguishing the arc. That is, the arc is forced up into but one of thefour spaces which it may normally enter, is squeezed between thesurfaces of the plates defining the space, and is extinguished therein,

The are in addition to being initially compressed in one or two of theslots or spaces between the plates is intercepted transversely by theplurality of metallic surfaces which define the strips or bars 60. Thesestrips or bars 60 which are of highly conductive material, preferablycopper, tend to break the are up in series among them. That is, shouldthe arc be squeezed, say, into the slot 85, it will encounter a numberof strips or bars 60, as shown by the dotted line 90, and will be brokenup into a series of small arcs between these strips or bars.

In addition, as the arc'is driven upwardly, the initial small seriesarcs will go out and new arcs, as indicated at 9|, will be establishedacross other strips or bars, which effect a new cooling action on thearc. As the arc moves still further upwardly, it will encounter stillmore strips and bars and be broken up into a larger number of small arcsin series. This continuous tearing of the roots of the small arcs fromthe lower strips or bars and re-establishing the small arcs above thesmall arcs which have been extinguished, will render the arcs unstableand lead to quick extinguishment.

The surfaces of the strips or bars 60 will tend further to cool the arcwhile the arc roots move along from strip to strip, and will result inquick extinguishment of the arc. Not only does this action take placewithin the principal slot (for instance, 85) into which the arc is firstsqueezed, but by reason of the fact that the strips or bars extendthrough all of the slots, arcs may be set up in adjacent slots. Thus,for instance, when a small series are is drawn between any two of thestrips or bars, the current in that are may flow transversely throughthe chute (longitudinally through the strips or bars) into adjacentslots. The strips or bars are sufliciently close for the particularvoltage for which the circuit breaker is rated so that at thesubstantial interrupting currents involved, new arcs may flash overbetween the adjacent strips or bars in other slots when the arc rootsare torn away from the strips or bars in the original slot, thustransferring a portion of the arc to another and cooler slot andrendering the are as a whole even more unstable.

By this structure, therefore, the arc is first squeezed into one or moreslots which extend parallel to the arc path and into which the are as awhole is squeezed between insulating plates. When squeezed into theslots between these insulating plates, the arc encounters a large numberof spaced transverse strips or bars. These strips or bars break the areup into a series of small arcs between them and by reason of the rapidmovement of the arc with respect to the surfaces of these strips or barsand upwardly from strip to strip, tend to cool the roots of the smallseries arcs. This tends quickly to extinguish the arc.

Furthermore, since each strip or bar extends through all of the slots,there is a tendency for the current to flow along the strips or bars andfor a small arc to strike over between closely adjacent strips or barsor another slot when the arc roots are torn from the same strips or barsin the original slot, thus forming some of the series arcs in a coolerslot, again rendering the arcs highly unstable and tending quickly toextinguish them.

This combination of squeezing the are between insulating plates,intercepting the arc by metallic members or strips or bars, breaking thearc up into a plurality of small arcs in series with each other andcausing some of the small arcs to strike over in adjacent slots, resultsin a very quick extinguishing action.

A great amount of back pressure often develops owing to the gases underhigh pressure which are confined in the narrow space. This back pressurehas been to some extent alleviated by providing communicating holesbetween the plates.

I have found that, in addition to their primary function of breaking thearc into a series of small arcs, the metallic strips or bars Gil providea conductive path between the spaces between the various plates, andaids materially in the extinw guishing of the arc.

As will be obvious from Figures 1 to 3, the insulating supporting plates.2! carry on their outer surfaces iron plates 95, 95. The are itselfforms a half turned current loop, and the magnetic field thus created isreinforced by the iron plates 95, 85 to drive the arc upwardly withgreat rapidity. Thus, in appropriate cases, all of the strips or bars 60may be of copper.

In Figures 3, 4 and 5, the formation of the strips or bars I00 in theupper two rows, of iron ing strips or bars I. The iron strips or barsrather than of copper, may reinforce the blowout effect. However, thearc chute may, in appropriate cases. comprise only copper strips orbars. Where only such copper strips or bars are used, then, ifnecessary, or desirable, a blowout magnet, such as that shown in myPatent No. 2,348,228, or in my application Serial No. 550,179 may beused.

Interphase barriers ll may be provided between adjacent poles whichusually have individual are I chutes. Such interphase barriers willprevent any flash-over oi the are from one pole to the other. The arechute is supported at the front of the circuit breaker by the frontlower edges of plates II which rest in the-slots O1, 9'! of thesupporting bridge 5|. The back of the arc chute is supported by the hook39 which engages the hook 40 of the arcing horn 4|.

The arc chute II is locked in place by the bolt 43 which engages theflange 4!. The arc chute may be readily removed for inspection andrepair, or for replacement of other elements of the circuit breaker,simply by rotating bolt 48 so that it will disengage flange 4!. Uponsuch disengagement, the arc chute may simply be pulled forward andremoved. The strips or bars 60 and plates 23 to 21 are preferablyassembled together first as a unit and then assembled with the arc chuteby placing the plate and strip or bar assembly between the plates 2| andpassing the bolts 30 to 33 through aligned openings in the plates.

As shown in Figures 1 and 2, the transverse copper strips or bars may bearranged in planes parallel to each other but are preferably staggeredwith respect to each other in order that their edges may betterintercept the arc. The plurality of transverse strips or bars 60 thuscorrespond to a multiplicity of transverse metallic arc extinguishingplates. The primary distinction, however, is that when the arc is brokenup serially, then instead of the roots of the small series arcs movingcontinually over a single plate,,

the heat of which may be substantially increased by the arc, the rootsof the small arcs are continually torn from one narrow plate or stripand transferred to another and cooler plate or strip. This combinationof continual transference to successive cool plates, and the continualtearing of the roots of the small arcs from one plate and forcing thesame over to other successive plates adds materially in the extinctionof the arc.

While the arrangement of the strips or bars iii of Figures 1 and 2 ispreferred, these strips or bars may be vantageously arranged inradiating form, as shown by the arrangement of the strips or bars ll ofFigure 6. The advantage of the arrangement of Figures 1 and2 is that thearcing first encounters but one or two of the transverse strips or barsand is thus gradually broken first into a pair of arcs in series;

then into three or four arcs in series, and then into a multiplicity ofarcs in series.

In the construction shown in Figure 6, the arc may initially be brokeninto a large number of arcs in series. This will introduce the coolingeffect much more rapidly but may somewhat retard the initial rapidmovement of the are into the chute.

In the construction shown more clearly in Figures 3 and 4, I have shownthe upper two rows of strips or bars Ill as being made substantially ofiron rather than of copper as are the remain- I have substantially thesame cross section and arrangement as the copper strips or bars 60, buthave an insulating sleeve or coating IOI over which is placed a coppersleeve or coating I02.

The copper sleeveor coating I02 extends across the arc chute for thesame distance and in the same manner as the strips or bars 60 and thuspreferably'does not come into contact with the side walls 2|, 2|.

The insulating coating IOI extends at I03, I03 beyond the end of thecopper coating I02 and into the slots I04 in the insulatingv side walls2| of the are chute. This prevents the iron portions I00 of the barsfrom being contacted by the arc. The iron portions I00 of the arc extendat I05, I05 beyond the ends of the insulating sleeve or coating I03 andinto engagement with the inner surfaces of the ferrous plates 95 to forma complete U-shaped magnetic path 95l00-95 for which the arc constitutesa half turned current loop.

The inner surfaces of the plates 05, 95 may be provided with suitablegrooves or through slots to receive the ends I05 of the iron strips orbars I00. The iron strips or bars I00 may be used without the insulatingcoating I03 or the conductive coating I02, and the conductive coatingI02 may even be placed directly around the iron strip or bar I00 withoutthe interpolated insulating coating I03. In this latter case, it wouldthen 'be preferred that the iron strips or bars I00 should not extend upto or through the insulating side walls 2|, 2| and small air gaps wouldthen exist between the ends of the bar I00 and the plates 95. Theblow-out eifect would not be as great as that in the construction shownin Figures 3 and 4 but will be effective for circuit interrupters of lowcapacity.

By the construction here shown, however, every one of the transversestrips or bars 60 and I00 has a cooling efiect, and, in fact, thecooling effect of the upper strips or bars I00 is enhanced since thecopper coating I02 has a somewhat greater surface than the surface ofthe copper strips or bars 60. The strips or bars 60 constitute in effecta multiplicity of small transverse plates supported by a plurality ofinsulating members and provide a greater surface and a greater coolingeffect than has been possible in the case of the continuous transverseplates of the prior art.

In the foregoing, l. have described my invention in connection only withspecific preferred embodiments thereof. Many modifications andvariations of my invention within the limitations of the foregoingdisclosures should now be obvious to those skilled in the art.Accordinglyfl prefer to be bound not by the specific disclosures hereinbut only by the appended claims.

I claim:

1. An are chute comprising means for drawing an arc, means for movingthe arc into the chute, and are extinguishing means within the arcchute; said are extinguishing means comprising a plurality of plates ofuniformly spaced insulating material mounted so that their planes arelongitudinal to the arc path and a plurality of metallic plates ofrectangular cross-section, each of said metallic plates extendingthrough the plates of insulating material and the spaces therebetween inthe path of and transverse to said are path as it enters said are chute.

2. An arc chute comprising means for drawing an arc, means for movingthe are into the chute, and are extinguishing means within the arcchute; said are extinguishing means comprising a plurality of uniformlyspaced plates of insulating material and a plurality of metallic plates,each of said metallic plates extending through the plates of insulatingmaterial and the spaces therebetween transverse to said are path; thesaid metallic plates being of rectangular cross-section andsubstantially parallel to each other with their edges disposedsubstantially toward said arc, the plurality of said insulating platesbeing transverse to the metallic plates and in the spaces intermediatethe ends of said metallic plates.

3. An arc chute comprising means for drawing an arc, means for movingthe arc into the chute, and are extinguishing means within the arechute; said are extinguishing means comprising a plurality of uniformlyspaced plates of insulating material and a plurality of metallic plates,each of said metallic plates having a rectangular cross-section andextending through the plates of insulating material and the spacestherebetween transverse to said are path; said metallic plates beingarranged in a plurality of rows and having their edges directed towardthe arc; the plurality of said insulating plates being transverse to themetallic plates and in the spaces intermediate the ends of said metallicplates.

4. An arc chute comprising means for drawing an are, means for movingthe are into the chute, and are extinguishing means within the arcchute; said arc extinguishing means comprising a plurality of uniformlyspaced plates of insulating material and a plurality of metallic plates,each of said metallic plates extending through the plates of insulatingmaterial and the spaces therebetween transverse to said are path; saidmetallic plates having a rectangular crosssection and being arranged ina plurality of rows and having their edges directed toward the are;

the plates in any one row being staggered with respect to the plates inan adjacent row, the plurality of said insulating plates beingtransverse to the metallic plates and in the spaces intermediate theends of said metallic plates.

5. An arc chute comprising means for drawing an are, means for movingthe are into the chute, and are extinguishing means within the arcchute; said are extinguishing means comprising a plurality of uniformlyspaced plates of insulating material and a plurality of metallic plates,each of said metallic plates extending through the plates of insulatingmaterial and the spaces therebetween transverse to said are path; saidmetallic plates having a rectangular cross-section and being arranged ina plurality of rows and having their edges directed toward the arc; theplates in any one row being staggered with respect to the plates in anadjacent row; the surfaces of said plates extending in planessubstantially radiating from the point of initiation of the arc, theplurality of said insulating plates being transverse to the metallicplates and in the spaces intermediate the ends of said metallic plates.

6. An arc chute comprising means for drawing an arc, means for movingthe are into the chute, and are extinguishing means within the arcchute; said are extinguishing means comprising a plurality of uniformlyspaced plates of insulating material and a plurality of metallic plates,each of said metallic plates extending through the plates of insulatingmaterial and the spaces therebetween transverse to said are path;

9 said metafiic plates having a rectangular crosssection an arranged ina plurality 01' rows and having thflr edges directed toward the arc;

the plates in any one row being staggered with lic plates.

WILLIAM M. 50011, JR.

10 ammcns 0mm The following references are of record in the file of thispatent:

UNITED STATES PATENTS Number Name Date Traver Jan. '7, 1930 Baker Sept.5,1933 Jennings Sept. 24, 1935 Baker Feb. 14, 1939 Pokorny Feb. 23, 1943

